The present invention relates to electrostatographic printing apparatus and more particularly to blade cleaning apparatus for use in such a printing system.
U.S. Pat. Nos. 4,690,544 and 4,681,426 describe and illustrate an electrostatographic printing machine with a removable imaging cartridge which has a belt type imaging surface or photoreceptor with a cleaner housing to remove residual toner material at about the twelve o'clock position on top of the belt. This geometry generally provides satisfactory cleaning and is used in the Xerox 5028 family of products. However, with an increasing desire for further cartridge life, additional cleaning capacity in the cleaner housing is required. In an extended life situation cleaning failure usually takes place according to two modes. Fine line cleaning failures are usually caused by debris such as paper fibers or other small particulate matter that become trapped under the cleaning blade which allows toner to pass under the blade ending up as a streak on the final print. Nicks or tears in the blade also cause fine line failures, but at much lower rate. Broadband cleaning failures occur due to an overfilled condition in the cleaning sump. During cleaning the area in front of the blade tip becomes filled with toner which is constantly in motion and gradually builds up on top of the blade (in a volcano-like fashion) compressing itself upon itself and producing a packing density of toner higher than the normal density of toner. In addition, the cleaning action generates heat and since the cleaner is in relatively close proximity to the heated fuser and precharge erase exposure lamp, the combination of compression due to cleaning force and heat promotes toner agglomeration so that the toner does not readily flow away from the cleaning blade. Ultimately as new toner comes in and tries to move up the face of the cleaning blade and away from the photoreceptor, the blade/imaging surface interface experiences forces reflected down from the toner mass buildup above the blade that changes both the blade tip geometry with respect to the imaging surface and the actual blade force on the imaging surface. As a result, the blade begins to plane on the toner on the imaging surface and the toner passes under the blade which has been lifted off the imaging surface. This begins as a grey patch that comes and goes, but eventually is continuous and gives a wide deposit of toner on the final print.